Roadway type luminaires commonly used for the lighting of streets and highways generally have a curved rounded back or top side and a medially humped bottom side with a refractor supported in its front portion. The bottom side is usually arranged to swing or pivot open to give access to the optics or to the electrical components, whence the name clamshell. The luminaire is usually mounted through a rear slipfitter on a pipe standard projecting upwardly from a lighting pole; as seen from below it bears some resemblance to a cobra with head raised, whence the alternative name.
Roadway luminaires must be packaged for shipping from factory, to warehouse, to service shop, to job site, and shipping is generally by truck in which space is at a premium. The refractor is of glass or clear plastic and, on account of its fragility, must be dismounted from the housing and protectively wrapped. Up to the present, what has generally been used is a wide corrugated paperboard carton in which the luminaire is supported bottom side against a broad side of the carton. Fillers are used as wedges to hold the luminaire housing in place and the refractor is included in the same carton and protected by an elaborate glass wrap filler.